This invention relates generally to polyphase code systems and more particularly to digital systems having reduced complexity for coding and decoding sequences of polyphase encoded signals.
In applications such as radar mapping and ranging, it is theoretically possible to achieve any desired range resolution by transmitting a sufficiently narrow pulse of energy and then processing the received energy in a receiver unit of suitable bandwidth. Following this approach, as the pulsewidth decreases the peak power of the transmitted signal must be increased if a given range capability is to be maintained. For many applications the combined range and range resolution requirements would require a transmitted narrow pulse of such peak power as to exceed the current voltage breakdown in transmission lines and antennas.
The above-described problem prompted the development of pulse compression techniques wherein a fairly long (time duration) low peak power encoded pulse is transmitted, and on reception the received signal is decoded (time compressed).
A discussion, including a full bibliography of phase-coded pulse compression techniques and the selection of optimum coding is provided at pages 428-32 of "Introduction to Radar Systems" 2nd. Ed. by Skolnik published by McGraw-Hill (1980).
Prior art digital decoding systems for encoded signals employ pseudo-random binary or polyphase codes such as the Frank code that do not have mirror symmetry between the first and last half of the code. As a consequence, the decoding systems require many components.